The number of UK small businesses making phone calls over the internet is set to double over the next year, according to research carried out for BT.
The company said the number of firms using VoIP will rise from the current 25% to 48%.
Research by Vanson Bourne found London leading the way, with 33% of small businesses already plugged in to the lower-cost call structures, followed by the North East of England (24%) and the South West (23%).
But Wales lags behind, with only 5% of firms currently using the technology, and only 7% planning to adopt VoIP in the next year.
Yet Northern Ireland, which routinely joins Wales at the bottom of UK internet adoption tables, is most optimistic - half of businesses surveyed there plan on using VoIP in the next 12 months.
BT offers VoIP as part of a business broadband package.
Meanwhile, Ofcom has introduced new regulations for the growing sector to ensure consumers know whether they can dial 999 and directory enquiries from VoIP services. Many VoIP platforms do not allow customers to make emergency calls.